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The Tut river basin covers an area of 846 km 2 comprises of seven sub-watersheds namely Tuichar Lui, Dap Lui, Tlubing Lui, Chal Lui, Raiseh Lui, Telva Lui, Zawngek Lui. The drainage network of the sub watersheds was delineated and mapped using Survey of India toposheets and satellite imagery (IRS P6, LISS-III, FCC, Geocoded) on 1:50,000 scale. The morphometric analysis, digitization and statistical computation were carried out with the help of ArcGIS 9.3 software. The drainage network showed that dendritic and subdendritic with parallel drainage pattern spreads over the entire river basin. The highest stream order is the 6 th order and the maximum stream number is 2029 first order 441 second order, 105 third orders and so on. Drainage density ranges from 0.37 to 4.66, stream frequency range between 0.65 and 8.10 and drainage texture varies from 5.63 to 19.56 showed that the area is characterized by permeable soils, soft sedimentary rocks such as sandstones and siltstones/shales with narrow valleys, dense floral coverage and high relief. The mean bifurcation ratio ranges between 3.03 to 6.58 indicate strong structural control over the area. The elongation ratio of sub-watersheds in the range 0.34 to 0.90 depicts sub-watersheds are more or less elongated characterizes high relief and steep slopes. The relief ratio ranges from 0.013 to 0.184 reflects high relief in the study area. The present study is an attempt to understand the nature of drainage and topography of river basin in order to implement sustainable development and management plan and practices at sub-watersheds level. Remote sensing and GIS proved to be an efficient tool and techniques for this investigation.

The Mat Fault situated in the Eastern Himalayan Fold Belt was mapped around Mizoram and is oriented NNW to SSE. This region has experienced a number of earthquakes in the recent past that damaged settlements and triggered numerous landslides. A set of geomorphic parameters were analysed on both sides of the Mat Fault to understand the tectonic setting. The six geomorphic parameters include: elongation ratio, hypsometric analysis, asymmetry factor, transverse topographic symmetry factor, stream length‐gradient index, and valley floor‐to‐width ratio, and they were calculated for 20 fourth‐order sub‐watersheds. Out of 20 sub‐watersheds, 10 sub‐watersheds were selected from the northern block and 10 from the southern block. Hypsometric analyses show that all the sub‐watersheds have attained a mature stage of geomorphic cycle of erosion; and from the analysis of hypsometric curves, it is found that 16 of the sub‐watersheds might have been uplifted due to tectonic activity. The asymmetry and transverse topographic symmetry factor values also suggest tilting in different directions possibly due to obstruction by faulting. The anomaly of high stream length index values is also observed in different sub‐watersheds indicating neotectonic activity. Low values of the valley floor‐to‐width ratio (<0.5) suggest V‐shaped valley topography, which indicate vertical incision due to tectonic activity. On evaluating relative tectonic activity among 20 sub‐watersheds, it is found that 80% of sub‐watersheds in the northern block show relatively stronger tectonic activity than the southern block. The present work suggests that the study area is tectonically active, and the possibility that they were produced by seismic activity.